1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, a process cartridge and an electrophotographic apparatus which have the electrophotographic photosensitive member.
2. Description of the Related Art
As photoconductive materials (a charge generating material and a charge transporting material) used for an electrophotographic photosensitive member mounted on an electrophotographic apparatus, organic photoconductive materials have been energetically developed. Usually, the electrophotographic photosensitive members using an organic photoconductive material have a photosensitive layer formed by coating a support with a coating liquid obtained by dissolving and dispersing an organic photoconductive material and a resin (binder resin) in a solvent, and drying this coating liquid. The layer structure of the photosensitive layer usually has a lamination type (regular type) structure obtained by forming a charge generation layer and a charge transport layer from the support side in this order.
The electrophotographic photosensitive member using an organic photoconductive material does not satisfy all the properties needed for an electrophotographic photosensitive member. In an electrophotography process, various objects such as a developer, a charging member, a cleaning blade, paper and a transfer member (hereinafter, sometimes referred to as a “contacting member or the like”) are brought into contact with the surface of the electrophotographic photosensitive member. The electrophotographic photosensitive member is required to have properties of reducing deterioration of images caused by contact stress when the electrophotographic photosensitive member comes into contact with these contacting members. Particularly, in recent years, as durability of the electrophotographic photosensitive member is improved, it is desired that an effect of reducing deterioration of images caused by the contact stress be sustained.
With respect to relaxation of the contact stress, there is a proposal that a siloxane-modified resin having a siloxane structure in the molecular chain is contained in the surface layer of an electrophotographic photosensitive member coming into contact with the above-mentioned various contacting members. For example, Japanese Patent Application Laid-Open No. 2009-084556 discloses a polyester resin having a siloxane structure and a polyamide structure incorporated into it. Japanese Patent Application Laid-Open No. 2007-004133 discloses a technique for using a block copolymer resin material having a siloxane structure to form a domain in the surface layer of an electrophotographic photosensitive member. Similarly, Japanese Patent Application Laid-Open No. 2005-242373 discloses a technique for using a silicone material in the state where the silicone material is dispersed in the form of particles in a charge transport layer of an electrophotographic photosensitive member, and teaches that discharge breakdown is effectively prevented, and deterioration of images (black dots) can be suppressed.
However, Japanese Patent Application Laid-Open No. 2009-084556 discloses a copolymer resin of a polyamide resin and a polyester resin into which a siloxane structure is incorporated (organosiloxane copolymerized polyester amide resin). In the case where these resins are simply used for the electrophotographic photosensitive member, an aggregate of the charge transporting material may be formed in the polyester resin, causing inferior potential stability when the electrophotographic photosensitive member is repeatedly used. In Japanese Patent Application Laid-Open No. 2009-084556, the length of the siloxane chain is devised for improvement in transparency. Japanese Patent Application Laid-Open No. 2009-084556, however, does not describe forming a matrix-domain structure of one resin and other resin. Moreover, there is description about imparting water repellency. Thereby, initial slip properties are improved, but continuation of slip properties when the electrophotographic photosensitive member is repeatedly used is not sufficiently attained.
In the electrophotographic photosensitive members disclosed in Japanese Patent Application Laid-Open No. 2007-004133 and Japanese Patent Application Laid-Open No. 2005-242373, keeping electrophotographic properties cannot be compatible with continuous reduction in the contact stress.
A material disclosed by Japanese Patent Application Laid-Open No. 2007-004133 is a resin having a component with low surface energy and a matrix component in the same resin. It is shown that the component with low surface energy forms a domain to provide a low surface energy state. A siloxane moiety that manifests the low surface energy state has high surface migration properties (interface migration properties), and is likely to exist at an interface of the charge transport layer close to the charge generation layer. For this reason, the siloxane moiety may cause deterioration of potential fluctuation in a laminated photosensitive member. Also in the electrophotographic photosensitive member produced using a material described in Japanese Patent Application Laid-Open No. 2007-004133, potential fluctuation due to the above-mentioned factor may be produced.
Also in the photosensitive member disclosed in Japanese Patent Application Laid-Open No. 2005-242373 in which the silicone material is dispersed in a particle form in the charge transport layer, potential fluctuation caused by the above-mentioned factor may be produced due to the same surface migration properties (interface migration properties) as those above.